The formation of molecular crystals is one of the most exquisite examples of self-assembly and molecular recognition. Although simple rules describing molecular packing and preference for certain crystallographic space groups have been developed, universal guidelines for predicting crystal structure remain elusive and computational methods have proven unsuccessful because of the complexity associated with the numerous weak intermolecular interaction that regulate molecular assembly. Accordingly, the design of new crystalline organic materials often employs strategies that rely on empirical building block approaches in which crystal architecture is prescribed by structure directing groups that define a molecular symmetry that propagates into a prescribed crystal symmetry. This will be illustrated by a family of molecular frameworks, assembled by hydrogen bonding, that exhibit numerous framework topologies governed by the choice of the building blocks. The constancy of hydrogen bond connectivity in these frameworks, which results from the strength of individual hydrogen bonds coupled with low-energy deformations of hydrogen bonds, permits de novo design of crystals. Furthermore, the compliance of 2-dimensional hydrogen-bond networks permits isomerism between lamellar and tubular architectures, reminiscent of microstructures observed in "soft matter," prompting the question of whether principles of elasticity and curvature can be applied to organic crystals as they are in soft matter.